Have you tried increasing the memory limit as suggested after the plugin conflict test? Due to multiple features from different plugins, the presence of one may cause this issue like Ubermenu if your memory limit is too low. But I coldn’t confirm any of this as any of the login URL isn’t working.
Please provide the correct login URL and increase the memory limit. You can also try upgrading your PHP version to 5.6 or above, 7.0+ is more recommended and in case it’s still old. Just in case it uses some features not available from older PHP versions.